152 



DIGESTION. 



The Gastric Juice and Stomach Digestion, 



The stomach has long been recognized as the organ in which the 

 most important part of the digestive process is inaugurated, and in 

 which the essential chemical modifications of the alimentary matters first 

 take place. Its action consists in the production of a special digestive 

 fluid, the gastric juice, furnished by the glandular apparatus of its 

 mucous membrane. 



The gastric mucous membrane presents certain variations, both in its 

 general appearance and its intimate structure, in different portions of 

 the stomach. It is red in the cardiac and middle portion, paler in the 

 cardiac portion. It increases also in thickness from the cardia toward 

 the pylorus ; being, according to the measurements of Kolliker, about 

 half a millimetre thick in the cardiac portion, one millimetre in the 

 middle, and one and a half to two millimetres near the pylorus. Its 

 free surface is everywhere more or less uneven and marked with minute 

 ridges or eminences. In the cardiac portion (Fig. 39) these ridges are 

 reticulated with each other, so as to include between them polygonal 

 interspaces, each of which is encircled by a network of capillary blood- 

 vessels. In the pyloric portion Fig. 40) the eminences are more distinct 



Fig. 39. 



Fig. 40. 



Free surface of GASTRIC Mucous MEM- Free surface of GASTRIC Mucous MEM- 

 BRANE, viewed from above; from Pig's BRANE, viewed in vertical section; from 

 Stomach, Cardiac portion. Moderately mag- Pig's Stomach, Pyloric portion. More highly 

 nified. magnified. 



from each other, pointed in form, about one-tenth of a millimetre in 

 height, and generally flattened from side to side. In the human subject 

 these villus-like projections have even been found extending over the 

 whole surface of the gastric mucous membrane. Each one contains a 

 capillary bloodvessel, which returns upon itself in a loop at the extremity 

 of the projection, and communicates freely with adjacent vessels. 



The entire thickness of the mucous membrane of the stomach consists 

 of glandular follicles or tubules, some of which are simple in structure, 



